feat: add generated scene skill platform hardening

docs/superpowers/specs/2026-04-19-g3-residual-contract-closure-design.md

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+# G3 Residual Contract Closure Design
+
+> Date: 2026-04-19
+> Status: Draft
+> Parent Framework Plan: `docs/superpowers/plans/2026-04-19-scene-skill-102-full-coverage-framework-plan.md`
+> Parent Route: `Route 2: G3 / paginated_enrichment`
+> Parent Layer: `Layer C + Layer D`
+
+## Intent
+
+Handle the remaining `G3` fail-closed records that are still unresolved after the enrichment-request and export-plan child plans have finished.
+
+## Fixed Input Bucket
+
+Residual `G3 / paginated_enrichment` records after:
+
+1. `G3 enrichment-request closure`
+2. `G3 export-plan closure`
+
+Expected residual themes:
+
+1. `g3_runtime_scope`
+2. `join_key`
+3. mixed residual contract blockers
+
+## Allowed Files
+
+1. `src/generated_scene/analyzer.rs`
+2. `src/generated_scene/generator.rs`
+3. `src/generated_scene/ir.rs`
+4. `tests/scene_generator_test.rs`
+5. route-local residual inventory and report assets
+
+## Forbidden Files
+
+1. `tests/fixtures/generated_scene/scene_execution_board_2026-04-18.json`
+2. Route 3+ plan files
+
+## Expected Delta
+
+1. reduce the residual Route 2 bucket after the first two child plans
+2. or explicitly defer a smaller residual set with named blockers
+
+## Stop Rule
+
+Stop when:
+
+1. the residual Route 2 bucket is either materially reduced, or
+2. the remaining residual Route 2 scenes are explicitly named and deferred
+
+After this point, Route 2 is considered complete or deferred.
+